Chichijima Research Articles

小笠原諸島父島から採集されたクチボソボラ Neomyxus leuciscus 稚魚と その生物地理学的考察

小笠原諸島父島から採集されたクチボソボラ Neomyxus leuciscus 稚魚と その生物地理学的考察

Conservation genetics of critically endangered Crepidiastrum grandicollum (Asteraceae) and two closely related woody species of the Bonin Islands, Japan

Crepidiastrum grandicollum is a critically endangered insular endemic herb found only on two oceanic islands of the Bonin Islands in Japan, namely Chichijima Island and Anijima Island. It is explicitly threatened by herbivory pressure from introduced animals. In 2009, a conservation program for C. grandicollum was begun to ensure its future persistence. To provide further information for conservation planning, we investigated the genetic diversity of C. grandicollum using 13 novel microsatellite markers in 55 individuals from four wild populations and an ex situ living collection. Two closely related woody species were also included for interspecific comparison: seven individuals of Crepidiastrum ameristophyllum and 13 of Crepidiastrum linguifolium. The 13 markers were applicable to all three species and identified 129 alleles in total. We found a clear genetic differentiation between C. grandicollum from Anijima Island and Chichijima Island. Crepidiastrum grandicollum also had low expected heterozygosity and allelic richness in populations compared to the two closely related species. Reconstructed divergence history suggested that differentiation between the islands had occurred several thousand generations ago. We suggest separate conservation units for C. grandicollum on Anijima Island and Chichijima Island given the clear (and putatively historical) genetic differentiation, which may result in speciation in the future.

Extreme gravity: Geologic effects

The maximum positive combined effect on the earth's gravity field of all geologic sources present in a given area, including any isostatic compensation, is limited by the ability of the lithosphere to support load. Bouguer gravity is one possible proxy for this effect. Bouguer maxima close to +350 mGal have been measured on Chichijima Island and Penrhyn Atoll in the Pacific Ocean. These may be the highest values anywhere on the planet. Suggestions of even higher values in the northernmost segment of the Colombian Andes rely on extrapolation of trends established in areas surrounding the Santa Marta Massif and must be treated with caution.

Sphaerillo boninensis Nunomura, 1990 (Crustacea, Isopoda, Oniscidea) is a junior synonym of a pantropical species, Venezillo parvus (Budde-Lund, 1885).

Re-examination of the holotype and paratype of Sphaerillo boninensis Nunomura, 1990 from Chichijima Island of the Ogasawara archipelago, which is registered as a UNESCO World Heritage Site, indicates that this species is a junior synonym of a pantropical species, Venezillo parvus (Budde-Lund, 1885).

Population genetic analysis of two species of Distylium: D. racemosum growing in East Asian evergreen broad-leaved forests and D. lepidotum endemic to the Ogasawara (Bonin) Islands

Although the genetic structures of populations in several model organisms have been studied even at the genomic level, quite a few ecologically important or evolutionary interesting species, such as endemic species on oceanic islands, exist whose genetic variations have not yet been studied. Genetic studies of those species may add new insights to our knowledge of evolution, especially when accompanied with ecological and geological knowledge of the species. In this study, we analyzed the genetic variation of two related species of Hamamelidaceae, Distylium racemosum and Distylium lepidotum, living in different habitats and possessing distinctive morphological characteristics. Distylium racemosum is one of the dominant trees of broad-leaved evergreen forests in Japan, and D. lepidotum is a dominant shrub in dry scrub endemic to the Ogasawara Islands. We analyzed the nucleotide variation at 112 protein-coding loci in 95 samples for the two Distylium species and inferred population structure and demographic history on the basis of these data. Our results showed that the samples from two Distylium species were genetically clustered into the following three groups: D. racemosum, D. lepidotum in the Chichijima Island, and D. lepidotum in the Hahajima Island. Furthermore, D. racemosum appears to have diverged first approximately 10 million years ago (MYA), and, then, the split of two populations of D. lepidotum occurred around 1 MYA. Additionally, we detected a few candidate loci that may contribute to adaptation of the species or local populations by exploring the pattern of the variation within and between species using the FST-outlier approach.

Strong genetic structure revealed by microsatellite variation in Callicarpa species endemic to the Bonin (Ogasawara) Islands.

Adaptive radiation is the diversification of a founding population into multiple taxa that are differentially adapted to diverse ecological niches. The three Callicarpa (Lamiaceae) species endemic to the Bonin Islands are considered to represent an example of adaptive radiation on oceanic islands. All three species are distributed in the Chichijima Island Group and grow in different habitats, while only one species, C. subpubescens, is distributed among other island groups. Particularly, in the Hahajima and Mukojima Island Groups, C. subpubescens grows in various habitats and shows relatively high morphological variation. We investigated genotypes of the three Callicarpa species at 14 microsatellite markers to elucidate genetic differentiation within and between species or island groups and between different habitats or morphologies. We found that genetic differentiation within C. subpubescens in the Hahajima and Mukojima Island Groups was equally as high as that between the three species in the Chichijima Island Group, while differentiation within C. subpubescens in the Chichijima Island Group was much lower. Analyses such as a Bayesian clustering analysis showed that genetically distinct groups were associated with the three species in the Chichijima Island Group, whereas they showed strong genetic structure within C. subpubescens in the Hahajima and Mukojima Island Groups among different habitats and morphologies. These results indicated that ecological diversification occurred in the Hahajima and Mukojima Island Groups. Meanwhile, high genetic differentiation among different island groups was also observed, reflecting isolation by distance. It implies that non-ecological factors such as geographic isolation also played important roles in genetic differentiation in Callicarpa species in the Bonin Islands. These findings suggest that the Callicarpa species in the Bonin Islands are differentiated into multiple genetic groups by both ecological and non-ecological factors.

What “the 50th Anniversary of the Reversion” of the Oagsawara Means: History of Chichi Jima and Iwo Jima since 1968

What “the 50th Anniversary of the Reversion” of the Oagsawara Means: History of Chichi Jima and Iwo Jima since 1968

Redescription of Dendrochirus zebra (Scorpaenidae: Pteroinae) with a new species of Dendrochirus from the Ogasawara Islands, Japan

Dendrochirus zebra (Cuvier in Cuvier and Valenciennes 1829) (Scorpaenidae: Pteroinae) is redescribed on the basis of 405 specimens from the Indo-West Pacific region. The species is diagnosed by the following combination of characters: dorsal-fin soft rays usually 10 (rarely 9 or 11); anal-fin soft rays usually 6 (rarely 5 or 7); pectoral-fin rays usually 17 (rarely 15, 16 or 18); scale rows in longitudinal series 45–57; three barbels on snout tip; pectoral-fin rays with up to two branches (maximum) throughout life; and distinct horizontal T-shaped (rotated 90° counterclockwise) marking on caudal peduncle. Dendrochirus sausaulele Jordan and Seale 1906 is regarded as a junior synonym of D. zebra. A syntype of Pterois zebra from Mauritius is designated as lectotype of the species. Dendrochirus koyo sp. nov. is described on the basis of a single specimen from 143 m depth off Chichi-jima Island, Ogasawara Islands, Japan. The new species is characterized by 10 dorsal-fin soft rays, 7 anal-fin soft rays, 18 pectoral-fin rays, 51 scale rows in longitudinal series, 3 barbels on the snout tip, and a K-shaped marking on the caudal peduncle. Notes are included on the status of “Pterois zebra” Quoy and Gaimard 1825 and “Brachypterus” sensu Catala 1964.

Species composition of coastal vegetation dominated by a non-native invasive species Imperata cylindrica var. koenigii on Chichijima Island, Ogasawara Islands, Japan

Species composition of coastal vegetation dominated by a non-native invasive species Imperata cylindrica var. koenigii on Chichijima Island, Ogasawara Islands, Japan

Long-Term Changes in the Dominance of Drought Tolerant Trees Reflect Climate Trends on a Micronesian Island

Background: The Ogasawara (Bonin) Islands of Micronesia lie in the western Pacific Ocean and are unique in terms of their isolation, climate, soils and diversity of rare plant species. We hypothesized that the vegetation on the islands will be a robust model system to study long-term climate change impacts on vegetation dynamics.
 Methods: A large, long-term vegetation monitoring plot was established on Chichijima Island and measured in 1976 and 2017. It was located in an undisturbed dry forest area that contained many endemic and endangered species.
 Results: During the 41 year study period, total basal area of tree species increased by 24.6% and was dominated by Schima, Distylium and Pouteria, whereas tree density declined by 30%. Tree genera exhibiting the largest increases in basal area were Elaeocarpus, Ilex, Pandanus, Pouteria, Rhaphiolepis, Syzgium and Schima. During the study period, the annual average (23.2ºC), minimum and maximum temperatures increased by 0.5 to 0.8ºC, respectively. The average annual precipitation was 1276 mm with severe droughts occurring in 1980, 1990 and 2016. The largest increases in the basal area were exhibited in trees species with wide functional distribution and attributes, including drought tolerance.
 Conclusions: The results of this study suggest a link between the drought tolerance, species dominance and climate change at the study location. Our unique approach of linking functional attributes with long-term vegetation and climate change can serve as a model for other studies of global change impacts.

Seasonal variations of low molecular weight hydroxy-dicarboxylic acids and oxaloacetic acid in remote marine aerosols from Chichijima Island in the western North Pacific (December 2010–November 2011)

Concentrations of homologous hydroxy-dicarboxylic acids (diacids) (hC3-hC6) and keto-diacid (oxaloacetic acid) were measured in the atmospheric aerosols collected at Chichijima Island (27.04° N, 142.13° E) in the western North Pacific from December 2010 to November 2011. The monthly averaged concentrations of hydroxy-diacids and oxaloacetic acid were significantly higher in spring followed by winter and autumn. Molecular distributions of hydroxy-diacids demonstrated that malic acid was the most abundant species in all four seasons, followed by tartronic acid in winter and spring and 3- and 2-hydroxyglutaric acids in summer and autumn. Hydroxy-diacids and keto-diacid maximized in spring and winter when air masses originated from the Asian continent with westerly winds. The concentrations of total hydroxy-diacids and oxaloacetic acid ranged from 0.1 to 27.3 ng m−3 and <0.005 to 2 ng m−3, respectively. The enhanced concentrations of diacids and their intermediates in winter and spring are associated with a long-range atmospheric transport of pollutants from East Asia to remote Chichijima Island followed by photochemical processing of organic aerosols. Seasonal molecular distribution of hydroxy-diacids and oxaloacetic acid was found to be dependent on the source strengths and plausible photochemical processing to form smaller diacids. Moderate to strong correlations among hydroxy-diacids, oxaloacetic acid and low molecular weight (LMW) diacids suggest that hydroxy-diacids and oxaloacetic acid are the intermediates in the photochemical oxidation of LMW diacid. Hence, photochemical formation of the most abundant LMW diacids, i.e., oxalic acid, could be produced from hydroxy- and keto-diacid as intermediates.

Thirteen years of observations on primary sugars and sugar alcohols over remote Chichijima Island in the western North Pacific

Abstract. In order to understand the atmospheric transport of bioaerosols, we conducted long-term observations of primary sugars and sugar alcohols over remote Chichijima Island in the western North Pacific from 2001 to 2013. Our results showed that concentrations of total sugar compounds for 13 years ranged from 1.2 to 310 ng m−3 (average of 46 ± 49 ng m−3). We found that atmospheric circulations significantly affect the seasonal variations of bioaerosol distributions over the western North Pacific. The primary sugars (glucose and fructose) maximized in summer, possibly due to an increased emission of the vegetation products from local vascular plants in Chichijima. We also found higher concentrations of sugar components (arabitol, mannitol, and trehalose) in more recent years during summer and autumn, suggesting an enhanced emission of fungal and microbial species over the island. Sucrose peaked in late winter to early spring, indicating a springtime pollen contribution by long-range atmospheric transport, while elevated concentrations of sucrose in early summer could be explained by long-range transport of soil dust from Southeast Asia to Chichijima. Sucrose and trehalose were found to present increasing trends from 2001 to 2013, while total sugar components did not show any clear trends during the 13-year period. Positive matrix factorization analyses suggested the locally emitted sugar compounds as well as long-range-transported airborne pollen grains, microbes, and fungal spores are the major contributors to total sugar compounds in the Chichijima aerosols. Backward air mass trajectories support the atmospheric transport of continental aerosols from the Asian continent during winter and spring over Chichijima.

Declining soil Crustacea in a World Heritage Site caused by land nemertean

Invasive non-native species are of great concern throughout the world. Potential severity of the impacts of non-native species is assessed for effective conservation managements. However, such risk assessment is often difficult, and underestimating possible harm can cause substantial issues. Here, we document catastrophic decline of a soil ecosystem in the Ogasawara Islands, a UNESCO World Heritage site, due to predation by non-native land nemertine Geonemertes pelaensis of which harm has been previously unnoticed. This nemertine is widely distributed in tropical regions, and no study has shown that it feeds on arthropods. However, we experimentally confirmed that G. pelaensis predates various arthropod groups. Soil fauna of Ogasawara was originally dominated by isopods and amphipods, but our surveys in the southern parts of Hahajima Island showed that these became extremely scarce in the areas invaded by G. pelaensis. Carnivorous arthropods decreased by indirect effects of its predation. Radical decline of soil arthropods since the 1980s on Chichijima Island was also caused by G. pelaensis and was first recorded in 1981. Thus, the soil ecosystem was already seriously damaged in Ogasawara by the nemertine. The present findings raise an issue and limitation in recognizing threats of non-native species.

Long-term (2001\u20132013) observations of water-soluble dicarboxylic acids and related compounds over the western North Pacific: trends, seasonality and source apportionment

To better understand the impact of East Asian pollutants on the molecular composition of marine organic aerosols, we conducted long-term (2001–2013) observations of water-soluble dicarboxylic acids and related compounds in total suspended particulate samples collected at Chichijima Island in the western North Pacific (WNP). Seasonal variations of all the diacids and related compounds showed maxima in winter and spring and minima in summer, except for azelaic acid (C9), which maximized in summer to autumn. The overall annual concentrations of the total diacids, ω-oxoacids and α-dicarbonyls showed an increase during 2001–2013. We found a significant (p < 0.05) decadal increase in the inter-annual trends of pyruvic and glyoxylic (p > 0.05) acids, and methylglyoxal (MeGly). In contrast, phthalic acid (p < 0.05) and glyoxal (Gly) showed a decrease in their trends. We also found a significant decrease in the trend of the Gly/MeGly mass ratios. These results demonstrate that the enhanced concentrations of diacids over the WNP are majorly attributed to the aqueous-phase photooxidation of biogenic volatile organic compounds from East Asia followed by long-range atmospheric transport. Further, positive matrix factorization analysis showed a biogenic photochemical contribution (42%) was the dominant source of oxalic acid in the WNP.

Rapid decline in pH of coral calcification fluid due to incorporation of anthropogenic CO2

Marine calcifying organisms, such as stony corals, are under threat by rapid ocean acidification (OA) arising from the oceanic uptake of anthropogenic CO2. To better understand how organisms and ecosystems will adapt to or be damaged by the resulting environmental changes, field observations are crucial. Here, we show clear evidence, based on boron isotopic ratio (δ11B) measurements, that OA is affecting the pH of the calcification fluid (pHCF) in Porites corals within the western North Pacific Subtropical Gyre at two separate locations, Chichijima Island (Ogasawara Archipelago) and Kikaijima Island. Corals from each location have displayed a rapid decline in δ11B since 1960. A comparison with the pH of the ambient seawater (pHSW) near these islands, estimated from a large number of shipboard measurements of seawater CO2 chemistry and atmospheric CO2, indicates that pHCF is sensitive to changes in pHSW. This suggests that the calcification fluid of corals will become less supersaturated with respect to aragonite by the middle of this century (pHCF = ~8.3 when pHSW = ~8.0 in 2050), earlier than previously expected, despite the pHCF-upregulating mechanism of corals.

Gilvossius chichijimaensis Sakai, 2015 (Crustacea: Decapoda: Axiidea: Callianassidae), a junior subjective synonym of Paratrypaea bouvieri (Nobili, 1904)

Sakai (2015) erected a new callianassid ghost shrimp taxon Gilvossius chichijimaensis diagnosed on the basis of Komai &amp; Tachikawa’s (2008) text and figures of a male specimen originally identified as Paratrypaea bouvieri (Nobili, 1904). A holotype was designated “CBM-ZC 7244, holotype male (cl 7.4 mm), Chichijima Island, Tokyo Prefecture”. This registration number appears to be a mistranscription from Komai &amp; Tachikawa’s (2008) list of specimens which includes “Chichi-jima Island: … CBM-ZC 7422, 2 males (5.2 mm, 7.4 mm), 1 ovigerous female (cl 6.9 mm), Okumura River, rivermouth, tidal flat, 7 August 2002,”. It can be assumed that the second male was selected as the holotype. Although Sakai (2015) did not designate paratypes, he based his comparison of the new species on “the male specimen (CMNH-ZC 2422) identified by Komai &amp; Tachikawa (2008) as Paratrypaea (= Gilvossius) bouvieri”, not the male he selected as holotype. By this he was probably referring to CMNH-ZC 2240.

小笠原村父島の浄水場における帯磁性イオン交換樹脂処理による水道水質の改善

小笠原村では水道水中のトリハロメタン (THM) や溶存有機物 (DOM) 濃度等が高いため, 父島の新浄水場の建設に伴い, 帯磁性イオン交換樹脂 (MIEX®) 処理を日本で初めて実際の浄水場に導入した。従来の活性炭・凝集沈殿処理後へその処理を導入したが, 凝集沈殿処理後への導入は前例がなく, 今回その効果を検証することを目的とした。その結果, 水道水中のTHMやハロ酢酸 (HAA) の前駆体及びDOC等の除去率が向上した。原水中のDOMの分子量は, 活性炭・凝集沈殿処理, さらにMIEX®処理により低下した。新浄水場の水道水中のTHMとHAAの濃度は, 旧浄水場の半分以下に減少した。小笠原村の新浄水場のMIEX®の設計段階におけるTHM及びTOCの目標値は, すべて達成された。

Hydroxy fatty acids in snow pit samples from Mount Tateyama in central Japan: Implications for atmospheric transport of microorganisms and plant waxes associated with Asian dust

AbstractWe report here the source apportionment of atmospheric soil microorganisms and higher plant metabolites based on chemical markers (hydroxy fatty acids: FAs) in the snowpack samples collected from Mount Tateyama in central Japan during spring 2009 (N = 6) and 2011 (N = 7). A homologous series of β‐hydroxy FAs (C9–C20), constituents of Gram‐negative bacteria (GNB), in snowpacks clearly suggest a long‐range atmospheric transport of dust‐associated bacteria followed by scavenging by snowflakes. Similarly, higher atmospheric abundances of α‐(C16–C32) and ω‐(C9–C30)‐hydroxy FAs in the snow layers containing Asian dust revealed contributions from soil microbes and higher plant epicuticular waxes. Moreover, covariation between the concentrations of hydroxy FAs and water‐soluble Ca2+ (dust tracer), together with calculated air mass backward trajectories, demonstrated their source regions such as the Taklamakan Desert, Gobi Desert, and Loess Plateau. A close match of molecular distributions of hydroxy FAs (with the predominance of ω‐ and β‐isomers) is noteworthy between snowpack (present study) and springtime aerosols from Chichijima Island in the western North Pacific (WNP). This observation suggests a “below‐cloud scavenging” of transported dust particles and associated soil microbes in the East Asian outflow by snowflakes. These distributions are, however, contrary to those observed in the fresh snow samples from Sapporo, northern Japan (predominance of α‐hydroxy FAs), which could be explained by “in‐cloud” microbial oxidation processes. This comparison, therefore, provides additional insights regarding the aeolian transport of soil microbes in the East Asian outflow to the WNP, which has not been available.

Development and evaluation of microsatellite loci for Gynochthodes boninensis (Rubiaceae), a woody climbing plant endemic to the Bonin (Ogasawara) Islands, Japan

Microsatellite loci were developed for Gynochthodes boninensis, an endemic climbing plant in the Bonin Islands. Using a Roche 454 GS Junior next-generation sequencer, 158 microsatellite loci were designed. Of the 48 microsatellite loci tested, 37 were successfully amplified and 25 were polymorphic in two populations of G. boninensis. For the 25 polymorphic loci, the mean expected heterozygosities per locus were 0.303 in the Chichijima Island population and 0.310 in the Hahajima Island population, respectively. There was no evidence of linkage disequilibrium in either population, but one locus showed significant deviation from Hardy–Weinberg equilibrium in one population. The microsatellite loci developed in this study will be useful for future studies of population genetics of G. boninensis. In particular, because this species is androdioecious (males and hermaphrodites coexist), characterizing the species gene flow is crucial to understanding the evolution and maintenance of this rare sexual system.

Minimum Longevity and Growth of the Invasive Green Anole,Anolis carolinensis, in Chichi-jima of the Ogasawara Islands, Japan

Abstract: We studied the longevity and growth pattern of the wild populations of invasive green anoles (Anolis carolinensis) in Chichi-jima Island, Japan. We estimated specimen age using skeletochronology and counted the number of lines of arrested growth (LAGs) on thin cross sections of femur bones. We observed from zero to five of LAGs for both male and female specimens. This indicated that the green anoles can survive at least five years in Chichi-jima Island. Body size increased with the number of LAGs, but the growth rate decreased when individuals had two LAGs. Our results suggest that the wild anoles might expend more energy for reproduction rather than for growth at this stage.